The present invention relates generally to a bushing and, more particularly, to a plastic bushing that can be used with a housing. The invention is particularly well suited for use in an engine compartment of a vehicle.
Electrical enclosures are used to hold electrical components, such as printed circuit boards and integrated circuits. For example, electrical enclosures hold the control modules for automobiles, such as the engine control module or the anti-lock braking module. The modules electronically perform many diagnostic and control functions.
As computer requirements have grown, manufacturers have begun to locate the modules closer to the equipment under evaluation. For example, modules are mounted in the engine compartment. Ideally, the enclosure effectively and inexpensively protects the control module from mechanical harm and the various environmental conditions accompanying a vehicular application.
One category of prior art enclosure uses an all-metal construction. The all-metal enclosure is typically made from die-casted aluminum or zinc and is assembled with an additional metal cover and screws. The enclosure shields the module from mechanical harm but is susceptible to the effects of humidity and liquid infiltration after repeated thermal cycling. To protect the module from the ambient environment, the all-metal enclosure is typically located within the passenger compartment.
The all-metal enclosure must be adapted to operate reliably outside of the passenger compartment. The adaptations include: over-coating the metal surface of the enclosure to reduce corrosion from the outside environment; implementing rattle-resistant fastening techniques to withstand the higher vibration found outside the passenger compartment; adding vibration and shock protection for the electrical components within the enclosure; and replacing the existing fasteners with other fasteners designed to reduce electrolytic contamination. The above corrections add cost to the module and only reduce the number of failures rather than eliminate them.
Another category of prior art enclosure includes a plastic housing. The prior art plastic housing possesses its own set of problems. For example, the plastic housing can crack or split if the bolts used to mount the enclosure are over-tightened. The prior art enclosure uses metal bushings with the plastic housing. The metal bushings are either pressed into the housing as a secondary operation or over molded during the production of the plastic housing.
However, the existing problems with the prior art all-metal enclosure also apply to the metal bushings. For instance, metal bushings must be plated with a corrosion resistant material to protect the bushings from environmental conditions. Further, the thermal coefficients of the plastic housing and the metal bushings are different. Thus, the ambient temperature causes the bushings and the housing to expand or contract at different rates, thereby creating gaps between the bushings and the housing. The overall improvements achieved by plastic housings are accordingly reduced by the use of metal bushings.
According to the teachings of the present invention, an enclosure can include a housing and a plurality of plastic bushings. The housing can be made from plastic and can be used to hold electrical components.
The inventive plastic bushing can be made from a temperature-resistant plastic and include a pair of ends, both with a countersink and an aperture, a bore passing between the apertures and parallel to the longitudinal axis of the bushing, and a flange with a poly-sided perimeter. The flange of the bushing engages the housing such that the bushing is fixed translationally and rotationally relative to the housing.
The bore can accept a fastener, such as a bolt, to retain the enclosure. The plastic bushing may be electrolytic-dissolution resistant and corrosion resistant. To resist creep, the plastic bushing may use a plastic that includes a plurality of fibers as a filler material. The fibers provide strength in the direction of stress and can be oriented parallel to the longitudinal axis of the bore of the bushing.
The present invention will become more readily apparent upon reading the following detailed description of exemplified embodiments and upon reference to the accompanying drawings herein.